Lift pump questions

dennhop · **Posted:** Wed Feb 22, 2012 1:24 pm

I've been reading through the lift pump threads, and noticed that most people tend to do the Cummins in tank pump conversion with the wiring harness mod. I know a bunch of people have asked the question of using a FASS or Airdog, but haven't really ogtten too far with that.
This is more for my own curiosity right now, as my lift pump appears to be working ok, and I'm not having any issues yet, but two questions on this:
which cord on the lift pump itself applies power to the factory lift pump in the engine bay? (IIRC, it is a lift pump as well as a fuel water separator/filter)

And for the Cummins mod, is that assembly being bypassed completely?

I was looking into it, and noticed on Airdogs website, that their duramax aftermarket lift pump is set to 8 psi from the manufacturer, which would be within the range of what the CP3a on the Liberty should require. I was considering, that when/if I needed to replace my pump, pulling the factory setup out of the engine bay, and seeing if the Airdog setup would fit in it's place. Assuming there's enough room, I'd only need to adapt the connectors on the 1/2 in lines, and I could use the Dodge in tank module modification for the fuel delivery part.

Any thoughts on this, or am I way off base? To me, this would seem simpler (assuming that it fits in the same spot) than to try and source all the other parts, and cut and splice wiring harnesses underneath the Jeep, as well as providing easily accessible fuel/water separators and fuel filters right there in the engine bay, that could be changed out with standard WIX or Fleetguard parts.

papaindigo · **Posted:** Wed Feb 22, 2012 3:21 pm

I think there is a bit of confusion here. The diesel fuel filter head and fuel pump/CP3 are 2 entirely separate things. The fuel pump/CP3 cannot be removed from the system and replaced with a separate pump as it's directly driven off the timing belt so removal would leave the TB short one pulley in its routing. The fuel filter head has 3 electronic contections: 1)WIF sensor on the bottom; 2) fuel temp sensor on passenger side top; and 3) fuel heater element driver's side top and it takes a standard WIX filter (33647) otherwise it's a passive system thru which fuel is pulled by the fuel pump/CP3.

The "problem" with the fuel delivery design on the CRD is that it uses a "puller" pump in the engine bay in conjuction with the gasser fuel lines that are designed to work with a "pusher" pump in the tank. Nothing wrong with the concept except the gasser fuel lines have quick disconnect fittings designed to keep fuel that's under presssure in not to keep air from creeping in when fuel is being pulled thru the lines. This combined with the tendency for the 1s gen OEM fuel filter head to experience a burned fuel heater element often results in air in the fuel lines. Since the fuel filter head it the high point in the system the air collects there and can 1) result in fuel starvation on startup (e.g. start and then die in a few seconds) and 2) possibly too little fuel going thru the fuel pump/CP3 which is bad as fuel is what lubes that system.

Solutions:
1) replace 1s gen fuel filter head and fuel heater wiring pigtail to prevent air leaks there - IMHO this should be done in anycase
2) don't bother with a lift pump just replace the (2 I believe) quick disconnect fittings in the fuel line - this combined with 1 should completely prevent air getting into the system short of running out of fuel.
3) add a supplimental "pusher" pump to the system to affirmatively move fuel and any induced air quickly thru the system. This can be done by 1) an intank pump which is the most difficult install but has the advantage of pressurizing the system so the quick disconnects can function as designed or 2) an inline lift pump either near the tank or in the engine bay which is cheap and easy and seems to work for most folks (Note - a variation on the inline in the engine bay adds a direct bleed to the fuel return line so that any air is dumped directly into the fuel return). The concensus on any supplimental pump is that it should to low psi, say 5-10, as higher psi may cause problems for the stock fuel pump/CP3 (lots of debate on how high is too high)

For me - step 1 took care of my problem but I have a Facet 40109 that I may install in the engine bay someday.

dennhop · **Posted:** Wed Feb 22, 2012 3:39 pm

So if I understand your answer, there is no lift pump in the CRD? The filter head in the engine bay is simply that then, nothing more than a fuel filter/preheater/water separator.

I understand the difference between the fuel pump and the filter, I guess where I may be confusing you is that I'm used to the Dodge Cummins design, where they have a lift pump, pulling fuel from the tank, and feeding it to the injection pump/CP3.

With your answer stating that there is no factory lift pump/pusher pump (I tend to call it a lift pump just due to my experience with the Cummins) the Airdog, if it can fit in the space left by the filter head, would work great to feed the CP3. This would allow me to replace all my stock lines to the tank with diesel rated rubber lines, replace my fittings, as well as provide a pump that will feed a steady 8 psi of non-aerated fuel to the CP3.

I'll have to start taking measurements off of my existing airdogs on both of my other trucks, as the dimensions will be the same as on the Dmax, and see if I can make it fit inside the engine bay with the factory filter head and assembly removed. I also need to start looking at how to trick the WIF sensor into reading correctly, while disconnected from the factory housing.

Does the fuel temp sensor have any affect on startup or operation of the CRD? If that's disconnected, will it throw any lights or codes?

papaindigo · **Posted:** Wed Feb 22, 2012 6:12 pm

I think we are still talking slightly past each other so:
1. yes the fuel filter head function is as simple as you describe
2. I'm familiar with the Dodge Cummins having owned 2 of them. What you are calling a lift pump on those vehicles is simply what I referred to as an intank pusher pump. Some have installed this type of intank pump as a suppliment to the CP3 but it requires dropping the tank to do so (unfortunately Jeep did away with the fuel tank access port that early KJs had in the back floor). There has been discussion of issues with excess psi output by some of the intank pump options.
3. others have installed what I tend to call a lift pump but might more accurately be called an auxiliary inline pump such as the Facet or a Kennedy both of which have low psi outputs. This option is cheaper and easier than the intank pump.

I'm not familiar with the Airdog although I did briefly glance at their Website. Is this a combination fuel filter/pump assembly? It looks like there is some mechanism to bleed off entrained air which might be nice. Might be an interesting setup although I think you can achieve the same ends for less $s and hassle. For example you can run diesel rated replacement fuel lines with the existing fuel filter head and get rid of the problemmatic quick disconnects. That step alone would probably take care of any entrained air problem especially with a 2n gen OEM head.

I have no clue about the WIF, fuel heater, or fuel temp sensor's interaction with the engine's "brain" if any. Although I can tell you running with the fuel heater unplugged doesn't trip and CEL.

Hoosier CRD · **Posted:** Wed Feb 22, 2012 7:43 pm

dennhop,

First off, welcome to the forum and the world of CRD ownership.

Now, as to your post: The Air Dog is an excellent system and can be used on most any diesel powered truck. That said, I don't think that there is enough room underneath the Liberty to install it properly, i.e. vertical. An Air Dog is meant to replace the factory in-tank lift pump and can be used in addition to the factory filtration. One can almost not ever have to much filtration. The Air Dog can be used with either a 10 micron fuel filter or a 2 micron. Most factory filters are 10 micron. If you are using a 2 micron at the Air Dog, your factory filter can last a very long time. The water seperator on the Air Dog is excellent.

The Raptor lift pump that you mentioned for the Duramax is set at 8 PSI as you noted. Still bulky, but much less so than the Air Dog. The factory filtration should be left intact. Being that the CRD engine also uses a CP3, yes, it is a logical choice to use.

Full disclosure: I work for a company that sells the Air Dog and Raptor. Not that that says a lot in and of itself. I have bought a Raptor lift pump to install on my Liberty. I have not gone so far as to check into the install just yet, but will likely tackle it soon. Hope this helps.

FWIW,

Hoosier CRD

P.S. FYI, the Raptor should be mounted as close the fuel tank as possible. In general, pumps push fluid much better than they pull fluid.

jws84_02 · **Posted:** Wed Feb 22, 2012 8:53 pm

If you are certain you have the first gen filter head, then I wouldnt think twice about doing a raptor or air dog in that location. but just like papa said, I don't know how the "brain" will react without the wiring hooked up. There is only one way to find out

I bought mine with the second gen filter head already on it and I haven't ever had a problem. If I ever do have a problem I will prolly go that route. Hopefully by then there will be more options for bigger injectors, turbos and tunes. Lol that way I can feel like the air dog is actually working and I can put on a show at scheids diesel estravaganza

ATXKJ · **Posted:** Wed Feb 22, 2012 9:22 pm

WIF and fuel heater can be disconnected.

however fuel temp - will trigger a limp mode if it doesn't have a good signal

dennhop · **Posted:** Wed Feb 22, 2012 10:34 pm

Hoosier CRD wrote:

dennhop,

First off, welcome to the forum and the world of CRD ownership.

Now, as to your post: The Air Dog is an excellent system and can be used on most any diesel powered truck. That said, I don't think that there is enough room underneath the Liberty to install it properly, i.e. vertical. An Air Dog is meant to replace the factory in-tank lift pump and can be used in addition to the factory filtration. One can almost not ever have to much filtration.

Hoosier CRD, where at in Indiana are you? I just moved from Indy. I have to say, whether or not you agree with me, but I love that state!

That being said, the only issue I see with trying to plumb an Airdog in and still using the factory filtration would be the pressure going through the filter housing. I know on Dodges they had a tendency to blow the housing on the factory fuel filter, but again, running a Dmax airdog, it might not be the same issue, as it's running a lower pressure.

jws84_02 wrote:

If you are certain you have the first gen filter head, then I wouldnt think twice about doing a raptor or air dog in that location. but just like papa said, I don't know how the "brain" will react without the wiring hooked up. There is only one way to find out

I bought mine with the second gen filter head already on it and I haven't ever had a problem. If I ever do have a problem I will prolly go that route. Hopefully by then there will be more options for bigger injectors, turbos and tunes. Lol that way I can feel like the air dog is actually working and I can put on a show at scheids diesel estravaganza

I'll do some more research, to identify if I'm running a 1st gen filter head or second gen filter head. I didn't catch on to the fact that there's a difference between the two of them.

Hoosier CRD · **Posted:** Thu Feb 23, 2012 7:19 am

Regarding fuel pressure, yes, you want to make sure that the pressure from downstream, e.g. Air Dog, Raptor, does not force fuel through any upstream filters,etc. With regard to the CRD, there is the vacuum/pull pump on the CP3. Having a pressure of no more than 8 PSI going to the fuel head should be fine.

The best way to verify what the pressure is at the head is to measure it of course; inlet and outlet sides and compare. The AirDog/Raptor is adjustable to some degree. Starting at no more than the 8PSI level, i.e. for a Duramax application, it is easily adjusted down if needed. Going from 15-17 PSI, like a Dodge setup, you likely will not have that amount of adjustability to get to at or below 8 PSI.

Keep in mind we are just feeding a stock 2.8 Liter engine here. The 100GPH capacity of the AirDog/Raptor is WAY overkill for our CRDs. You don't want to overwhelm the system, including the return, with too much pressure. Therefore less pressure is better. Hope this helps.

FWIW,

Hoosier CRD

papaindigo · **Posted:** Thu Feb 23, 2012 10:45 am

There is a fuel head bleeding video on Sam's NOOB guide that shows the difference between the 1s and 2n gen filter heads. 2n gen will have a spliced in new wire pigtail to the fuel heater plug and all the pigtails I've seen have a bright blue plug cap.

dennhop · **Posted:** Thu Feb 23, 2012 1:03 pm

I just caught that...1st time I watched the video, I had the kids and dogs running around like it was the end of the world, (or rather, the end of the school day) so I didn't make it to the end of the video. I'll go and check on mine, but I'm almost willing to bet that mines the 1st gen fuel head.

dennhop · **Posted:** Mon Apr 02, 2012 9:28 am

Finally got a chance this weekend to look at the pump, and I've got the second gen fuel head...two green wires, spliced into the factory wiring harness. One less thing I have to worry about right now.

dennhop · **Posted:** Thu Sep 06, 2012 8:44 am

I'm revisiting this thread again, as I'm noticing that I have a ton of air in my lines, enough to the point where the engine is dying while running, and giving me a hard start unless I get out and manually pump the filter head. Hoosier CRD, have you looked into installing your raptor 100 yet? I'm thinking about going that route, as it would allow me to not only add a lift pump to the system, but would give me the new fuel lines needed, to try and keep the system pressurized. This morning on the drive to work, the Jeep died on me about 6 or seven times, and when I pulled into the parking lot, I had to pump the filter head about a dozen times to rebuild pressure to the system.

ChooChooman74 · **Posted:** Thu Sep 06, 2012 9:04 am

This is similar to what I have. Works great since I installed it.

http://www.rockauto.com/catalog/moreinfo.php?pk=293418

jkbkwarner · **Posted:** Thu Sep 06, 2012 10:10 am

Two things:

1) Is the filter on secure, lubricated gasket and not a double gasket, meaning the previous filter change didn't leave the previous gasket sitting against the filter housing.

2) For me and others, it has been the added problem of the hose clips between the tank, and its plastic nipple fittings, and the metal lines to the engine compartment. I replaced those hoses with higher quality hoses, such as marine grade hoses (I think papaindigo's recommendation). And secure them with worm clamps. I haven't had air in my fuel since. :pepper:

dennhop · **Posted:** Thu Sep 06, 2012 1:24 pm

I have no fuel wetness around the filter/filterhead-other than where I was cracking the bleeder screw, but that's bone dry. I'm going to try and get a new filter, as well as new fuel line today, as soon as I get off work, and see if I can't fix the issue, once and for all tonight...wife's got an appt in Wilmington tomorrow, that she needs the Jeep for, so I have to have it running tonight. :banghead:

It always happens that way....

jkbkwarner · **Posted:** Thu Sep 06, 2012 1:30 pm

dennhop wrote:

I have no fuel wetness around the filter/filterhead-other than where I was cracking the bleeder screw, but that's bone dry. I'm going to try and get a new filter, as well as new fuel line today, as soon as I get off work, and see if I can't fix the issue, once and for all tonight...wife's got an appt in Wilmington tomorrow, that she needs the Jeep for, so I have to have it running tonight. :banghead:

It always happens that way....

You probably won't see a wetness around the filter head. It's not leaking out, it's drawing air in. Probably because the fuel is thicker than air and the hole is minuscule or we'd all use duct tape to solve it. :jester:

dennhop · **Posted:** Thu Sep 06, 2012 9:40 pm

So yeah, after 5 hours of sheer frustration, 10 gallons of diesel wasted, and luckily not finding a match, heres whats going on now.
Replaced the fuel lines btween the tank and the metal line with marine grade fuel line. Spent the next 4 hours trying to get the tank back on thanks to the tank straps. Tried bleeding system....fuel bleeder popped, and started leaking. Thats where i left it tonight

msilbernagel · **Posted:** Fri Sep 07, 2012 1:30 am

When I installed an in-tank fuel pump, I first drained the tank through the line in the engine compartment by connecting a cheap 12V fuel pump to it and draining into an external fuel can. Made manhandling the tank in and out of the straps much easier.

FYI - Mark

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